1. Field of the Invention
This invention relates to vehicle battery charging systems and, in particular, photovoltaic solar recharging cells for vehicle batteries.
2. Description of the Prior Art
Historically, automotive batteries have been used to power the starter of an internal combustion engine of most automobiles. Similar battery and starter systems are used for most other vehicles. The electromotive starter imposes a heavy load on the battery and each start of the engine drains the battery of a measurable portion of the stored energy in the battery. Alternators and generators recharge the battery while the engine is running. While the engine is not running, no substantial load was applied (until recent years) to the battery until the starter was operated to start the engine, which in turn, activated the alternator or generator to recharge the battery. Accordingly, the battery was not drained until immediately before the engine was started when the battery was recharged by the running engine. Since the battery was not subjected to any substantial load while the engine was off, at least until the starter was activated, the battery could retain sufficient charge indefinitely (for at least several months). Accordingly, in the distant past, batteries did not require charging while the engine was off, even when the vehicle was not started for several weeks or months.
In the recent past, many small electrical devices have been added to automobiles and other vehicles that draw electrical current while the engine is not running. For example, automobiles are equipped with digital clocks, courtesy lights, electronic security systems, computer systems, cellular telephones and mobile radios that require electrical power from the vehicular battery while the engine is not running. While the power drain of each of these devices may be relatively small individually as compared to the storage capacity of the battery, the cummulative effect of all of these devices, especially over an extended period of time, often times is sufficient to drain the battery of electrical energy such that the battery has insufficient power to start the engine. Accordingly, there has been a growing need over the last ten or more years for devices that charge vehicular batteries while the engine is not running.
The most common system for recharging automotive batteries is while the vehicle engine is not running is an external battery charger that plugs into a electrical wall socket and applies a low electrical charge to the battery with clamps attached to the terminal posts of the battery. The clamps of the battery charger are removed before starting the engine and driving the vehicle. This becomes a safety issue in that naturally-occurring explosive hydrogen and oxygen gases are present at the battery vents, and disconnecting the clamps can create a spark which could possibly ignite these gases and cause a battery explosion while a person is directly adjacent to the battery, thereby causing bodily harm. In more recent years, photovoltaic solar cells have been adapted to charge vehicular batteries. Such solar cells have been incorporated onto the surface of the metal or plastic skin of the roof, window surfaces or other upwardly facing segment of the vehicle body. Similarly, external solar cells are available that plug into a cigarette lighter of an automobile and apply a low charge to the battery.
In these prior attempts to adapt solar cells to charge a battery of a vehicle, the solar cells applied to the surfaces of the vehicle have suffered such disadvantages as being difficult to paint (most paints obstruct solar light that must reach the photovoltaic cells) or, if not painted, disgrace the appearance of the vehicle. External solar cells have the disadvantage that they must be manually set up each time the battery is to be charged and most people do not desire to be bothered with setting up such solar cells. In addition, most manufacturers of solar cells have packaged solar cells into protective units that are rigid and relatively thick. These solar cell units are attached to the vehicle. The resulting attached solar cell unit does not readily merge atheistically or practically with the vehicle. Instead, prior attempts to add solar cells to a vehicle have resulted in a highly visible solar cell attached to a vehicle. Accordingly, there is a long an resolved need for a solar cell system for charging vehicular batteries that does not disrupt the atheistical qualities of the vehicle.
Furthermore, prior to the current invention, thin film solar cells were not directly incorporated into the surfaces of a vehicle. Solar cells had to be packaged to protect the fragile and rigid cells before they were integrated into the vehicle. The packaging provided adequate shielding of the solar cell, but was difficult to integrate into the surfaces of the vehicle. To avoid some of the difficulties with packaged solar cells, there were prior art attempts to form solar cells on the surfaces of vehicle sunroofs by vacuum deposition of an amorphous silicon layer on the secondary glass surface. Amorphous silicon technology is well known to be the least efficient of the photovoltaic solar cell materials, and therefore, requires between 2 to 4 times as much exposed surface area be manufactured or incorporated into a vehicle surface to produce an equivalent amount of energy as this patent application describes. Amorphous silicon technology has several other disadvantages including that the solar cell layer on the outer surface of the glass is easily destroyed by being scratched or otherwise damaged. In addition, the electrical connections to the exposed surface layer are themselves exposed and susceptible to being damaged. Accordingly, these prior art techniques for adapting solar cells for use as vehicle battery recharges have proven to be less than satisfactory and have not frilly solved the need for a passive vehicle battery recharger.